An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Scattering of electromagnetic waves in solids and liquids when, as a result of the scattering process, an acoustic → phonon is emitted or absorbed. Brillouin scattering is analogous to → Raman scattering.

→ Brillouin zone; → scattering.

Crystallography: One of the several regions which, in reciprocal space, represent the solution of the wave equations for the propagation of → phonons or electrons in solids. The first Brillouin zone is the Wigner-Seitz cell of the reciprocal lattice. It is a polyhedron obtained by connecting a lattice point to its first neighbors and drawing the planes perpendicular to these connecting lines and passing through their midpoints. The second Brillouin zone is obtained by a similar construction but the second-nearest neighbours.

After Léon Brillouin (1889-1969) French physicist; → zone.

1) Water saturated or strongly impregnated with salt.
2) Any saline solution.

M.E. from O.E. bryne "brine," origin unknown; cognate with Du. brijn.

Aždem, from Gilaki and Tâti aždem "very salty water" used for preserving fish.

An international collaboration between Austria, Canada, and Poland, currently comprising five nano-satellites to investigate stellar structure and evolution of the brightest stars in the sky and their interaction with the local environment. BRITE is also used to study micropulsation, wind phenomena, and other forms of stellar variability. These nano-satellites aim to monitor stars brighter than V ~ 5 mag using two color pass-bands, over various observing campaigns. Each nano-satellite hosts a 3 cm telescope, providing a wide field of view (24° x 20°) to simultaneously observe up to a few dozen stars (Weiss et al. 2014).

BRITE, short for → BRIght Target Explorer; → bright; → target; → explorer.

A → substance that has a low → elastic limit. For example → glass, which breaks if its low elastic limit is exceeded.

M.E. britel, from brit-, akin to O.E. brytan "to crush, break to pieces," + -el adj. suffix.

Tord "brittle, fragile;" ultimately from Proto-Ir. *tard- "to split, pierce;" related to tâlidan (Dehxodâ) "to spoliate, plunder," eftâlidan "to tear, break," → dissipate; cf. Shughni tidarδ- "to tear, pluck," zidarδ- "to tear, break;" Skt. tard- "to split, to pierce."

Wide in extent from side to side.

M.E. bro(o)d, from O.E. brad; cf. O.N. breiðr, Du. breed, Ger. breit, Goth. brouþs.

Pahn "wide, broad," from Mid.Pers. pah(a)n; Av. paθana- "broad, wide, spacious;" PIE root *pete- "to spread;" cf. L. patere "to be open," Gk. petannynai "to spread out," petalon "a leaf."

Photometric measurements carried out through filters with a band-width (about one-tenth the central wavelength) in the range 30-100 nm. Typical examples are Johnson photometry, Krons-Cousins RI photometry, and the six-color system.

→ broad; → band; → photometry.

A radio galaxy that shows broad optical emission lines. → broad-line region.

→ broad; → line; → radio galaxy.

The inner region of a → quasar or an → active galactic nucleus exhibiting broad → spectral lines which indicate ionized matter moving with speeds in excess of 10,000 km sec^-1, probably due to the presence of an → accretion disk surrounding a → supermassive black hole. Also called Type I AGN. See also → obscuring torus.

→ broad; → line; → region.

To make or become broad or broader.

→ borad.

Pahnidan, from pahn, → broad, + -idan infinitive suffix.

The act of making something wider. → instrumental broadening; → line broadening.

Broadening, from → broad + → -ing noun froming suffix.

Pahneš, from pahn (→ broad, present tense stem of pahnidan "to broaden" + -idan infinitive suffix) + eš verbal-noun suffix.

Same as the → Coathanger and Collinder 399.

Named after the American amateur astronomer D. F. Brocchi who created a map of the cluster in the 1920s for calibrating photometers; → cluster.

A system of connected line → segments joined end to end.

Past participle of → break; → line.

The only liquid non-metallic chemical element; symbol Br. → Atomic number 35; → atomic weight 79.904; → melting point -7.2°C; → boiling point 58.78°C; → specific gravity of liquid 3.12 at 20°C; → valence -1, +1, +3, +5, or +7. A member of the halogen group of elements. Volatilizes readily at room temperature to a red vapor with strong disagreeable odor and very irritating effect on the eyes and throat. Occurs in combination with various metals, as potassium, sodium and magnesium bromides, which are found in mineral waters, in river and sea-water, and occasionally in marine plants and animals. Its compounds are widely used in photography and medicine. Discovered by Antoine-Jerome Balard (1802-1876) in 1826. Its two stable → isotopes are ⁷⁹Br (50.69%) and ⁸¹Br (49.31%).

From Fr. brome, from Gk. bromos for "stench, bad odor," coined by its discoverer.

Brom, loan from Fr., as above.

A class of → alloys in which → copper and → tin are the dominant elements. The name is extended by usage to include many other copper-rich alloys containing → phosphorus, → manganese, → aluminium, or → silicon.

From Fr. bronze, from It. bronzo, from M.L. bronzium, of unknown origin, maybe from Iranian, cf. Mid.Pers. brinj "bronze, brass;" Mod.Pers. berenj "brass."

Boronz, loan from Fr., as above. Mefraq, from Ar.

A period of time between the → Stone Age and the → Iron Age when bronze was used widely to make tools, weapons, and other implements. The Bronze Age starts at different areas of the world at different times. The earliest use of bronze for making farm tools and weapons are found in Near and Middle East and date back to about 3700 BC. The Bronze Age starts about 2300 BC in Europe.

→ bronze; → age.

Son of the same parents as another person.

M.E.; O.E. brothor; cognate with Du. broeder, Ger. Bruder, Goth. brothar, Skt. bhrātr, Gk. phrater, L. frater, Pers. barâdar, as below, Rus. brat; PIE *bhrater.

Barâdar, from Mid.Pers. brât(ar) "brother;" O.Pers. brata-; Av. brātar- "brother;" cognate with E. brother, as above.

A dusky color between red and black.

M.E. broun, from O.E. brun "dark," cf. Du. bruin, Ger. braun; PIE base *bher- "shining, brown," related to *bheros "dark animal" (cf. beaver, bear).

Qahvei-yi, color of qahvé "coffee."

A star-like object whose mass is too small to sustain → hydrogen fusion in its interior and become a star. Brown dwarfs are → substellar objects and occupy an intermediate regime between those of stars and giant planets. With a mass less than 0.08 times that of the Sun (about 80 → Jupiter masses), nuclear reactions in the core of brown dwarfs are limited to the transformation of → deuterium into ³He. The reason is that the cores of these objects are supported against → gravitational collapse by electron → degeneracy pressure (at early spectral types) and → Coulomb pressure (at later spectral types). Brown dwarfs, as ever cooling objects, will have late M dwarf spectral types within a few Myrs of their formation and gradually evolve as L, T and Y dwarfs → brown dwarf cooling. As late-M and early-L dwarfs, they overlap in temperature with the cool end of the stellar → main sequence (→ M dwarf, → L dwarf, → T dwarf, → Y dwarf). In contrast to the OBAFGKM sequence, the M-L-T-Y sequence is an evolutionary one. These objects were first postulated by Kumar (1963, ApJ 137, 1121 & 1126) and Hayashi & Nakano (1963, Prog. Theor.Phys. 30, 460).

The term brown dwarf was first used by Jill Tarter in her 1975 PhD thesis; → brown; → dwarf.

The process whereby a → brown dwarf cools over time after the → deuterium burning phase, which lasts a few 10⁷ years. The → effective temperature and luminosity decrease depending on the mass, age, and → metallicity. Even though massive brown dwarfs may start out with star-like luminosity (≥ 10^-3→ solar luminosities), they progressively fade with age to the point where, after 0.5 Gyr all → substellar objects are less luminous than the dimmest, lowest mass stars. More explicitly, brown dwarfs may start as star-like objects hotter than 2200 K, with → M dwarf spectral types, and, as they get older, pass through the later and cooler L, T, and Y spectral types (→ L dwarf, → T dwarf, → Y dwarf).

→ brown; → dwarf; → cooling.